U.S. patent application number 14/812038 was filed with the patent office on 2016-02-11 for chain continuously variable transmission.
This patent application is currently assigned to JTEKT CORPORATION. The applicant listed for this patent is JTEKT CORPORATION. Invention is credited to Teruhiko NAKAZAWA, Taizou WAKAYAMA, Shinji YASUHARA.
Application Number | 20160040761 14/812038 |
Document ID | / |
Family ID | 55135008 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160040761 |
Kind Code |
A1 |
YASUHARA; Shinji ; et
al. |
February 11, 2016 |
Chain Continuously Variable Transmission
Abstract
When a chain is wound around a pulley, a pin-pulley contact
point as a contact point of a pin of the chain with the pulley
slides and moves on a conical surface of the pulley. A contact
point slip distance, namely the distance by which the pin-pulley
contact point moves on the conical surface at this time, is
associated with an offset. The offset is the distance between a
pin-pin contact point, which is a contact point between the pins at
the time the chain is in a linear state, and the pin-pulley contact
point in a y-axis direction. Offsets that minimize the contact
point slip distance at the maximum running radius and the minimum
running radius of the chain are obtained, and the offset is set
between these values. The pin-pulley contact point is set close to
the pin-pin contact point of the chain in the linear state.
Inventors: |
YASUHARA; Shinji;
(Yamatokoriyama-shi, JP) ; WAKAYAMA; Taizou;
(Kashiwara-shi, JP) ; NAKAZAWA; Teruhiko;
(Nagakute-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JTEKT CORPORATION |
Osaka |
|
JP |
|
|
Assignee: |
JTEKT CORPORATION
Osaka
JP
|
Family ID: |
55135008 |
Appl. No.: |
14/812038 |
Filed: |
July 29, 2015 |
Current U.S.
Class: |
474/8 |
Current CPC
Class: |
F16H 9/20 20130101; F16G
5/18 20130101; F16H 9/24 20130101 |
International
Class: |
F16H 9/08 20060101
F16H009/08; F16H 9/24 20060101 F16H009/24; F16G 13/06 20060101
F16G013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 8, 2014 |
JP |
2014-162904 |
Claims
1. A continuously variable transmission, comprising: two pulleys
each having opposing conical surfaces and configured so that a
distance between the conical surfaces can be changed; and a chain
that is wound around the two pulleys and is held between the
conical surfaces, wherein the chain includes plate-like links each
having an opening and arranged in a circumferential direction of
the chain and is formed by coupling chain elements to each other,
each of the chain elements includes a link unit that is formed by a
plurality of the links arranged in a lateral direction of the
chain, and two pins that extend through both ends of each of the
openings of the links and that contact the conical surfaces at
their both ends, and the chain elements are coupled to each other
by inserting the pin of each chain element through the openings of
the links of another chain element adjoining in the circumferential
direction of the chain, offsets of the two pins are set between a
larger one of such offsets of the two pins that minimize a contact
point slip distance between a linear state and a maximum bent state
of the chain and a smaller one of such offsets of the two pins that
minimize the contact point slip distance between the linear state
and a minimum bent state of the chain, and the offset is a directed
distance of a pin-pulley contact point, namely a contact point of
the pin with the pulley, from a reference point in a thickness
direction of the chain, the reference point is a pin-pin contact
point, namely a contact point between the pins of each chain
element, at the time the adjoining chain elements are in the linear
state, and the contact point slip distance is a distance by which
the pin-pulley contact point moves with respect to the pulley when
the chain element is stretched and bent to be changed between the
linear state and a bent state where the chain element is wound
around the pulley.
2. A continuously variable transmission, comprising: two pulleys
each having opposing conical surfaces and configured so that a
distance between the conical surfaces can be changed; and a chain
that is wound around the two pulleys and is held between the
conical surfaces, wherein the chain includes plate-like links each
having an opening and arranged in a circumferential direction of
the chain and is formed by coupling chain elements to each other,
each of the chain elements includes a link unit that is formed by a
plurality of the links arranged in a lateral direction of the
chain, and two pins that extend through both ends of each of the
openings of the links and that contact the conical surfaces at
their both ends, and the chain elements are coupled to each other
by inserting the pin of each chain element through the openings of
the links of another chain element adjoining in the circumferential
direction of the chain, an offset of a first pin of the two pins is
set between such an offset that minimizes a contact point slip
distance of the first pin between a linear state and a maximum bent
state of the chain and such an offset that minimizes the contact
point slip distance of the first pin between the linear state and a
minimum bent state of the chain, an offset of a second pin of the
two pins is set between such an offset that minimizes a contact
point slip distance of the second pin between the linear state and
the maximum bent state of the chain and such an offset that
minimizes the contact point slip distance of the second pin between
the linear state and the minimum bent state of the chain, and the
offset is a directed distance of a pin-pulley contact point, namely
a contact point of the pin with the pulley, from a reference point
in a thickness direction of the chain, the reference point is a
pin-pin contact point, namely a contact point between the pins of
each chain element, at the time the adjoining chain elements are in
the linear state, and the contact point slip distance is a distance
by which the pin-pulley contact point moves with respect to the
pulley when the chain element is stretched and bent to be changed
between the linear state and a bent state where the chain element
is wound around the pulley.
3. A continuously variable transmission, comprising: two pulleys
each having opposing conical surfaces and configured so that a
distance between the conical surfaces can be changed; and a chain
that is wound around the two pulleys and is held between the
conical surfaces, wherein the chain includes plate-like links each
having an opening and arranged in a circumferential direction of
the chain and is formed by coupling chain elements to each other,
each of the chain elements includes a link unit that is formed by a
plurality of the links arranged in a lateral direction of the
chain, and two pins that extend through both ends of each of the
openings of the links and that contact the conical surfaces at
their both ends, and the chain elements are coupled to each other
by inserting the pin of each chain element through the openings of
the links of another chain element adjoining in the circumferential
direction of the chain, absolute values of offsets of the two pins
are equal to or smaller than 0.085 times a length of a projected
ridge of the pin, and the offset is a directed distance of a
pin-pulley contact point, namely a contact point of the pin with
the pulley, from a reference point in a thickness direction of the
chain, the reference point is a pin-pin contact point, namely a
contact point between the pins of each chain element, at the time
the adjoining chain elements are in a linear state, and the
projected ridge is a line formed by projecting on a plane
perpendicular to the lateral direction of the chain a line
connecting outermost points of an end face of the pin which faces
the pulley, namely those points of the end face of the pin which
are located closest to the pulley, in each section of the pin
perpendicular to the thickness direction of the chain.
4. The continuously variable transmission according to claim 1,
wherein the offset of each pin is set to such a value that a
contact point pitch at the time the chain is in the maximum bent
state is equal to or larger than that at the time the chain is in
the linear state, and the contact point pitch is a distance between
adjoining ones of the pin-pin contact points.
5. The continuously variable transmission according to claim 2,
wherein the offset of each pin is set to such a value that a
contact point pitch at the time the chain is in the maximum bent
state is equal to or larger than that at the time the chain is in
the linear state, and the contact point pitch is a distance between
adjoining ones of the pin-pin contact points.
6. The continuously variable transmission according to claim 3,
wherein the offset of each pin is set to such a value that a
contact point pitch at the time the chain is in the maximum bent
state is equal to or larger than that at the time the chain is in
the linear state, and the contact point pitch is a distance between
adjoining ones of the pin-pin contact points.
Description
INCORPORATION BY REFERENCE
[0001] The disclosure of Japanese Patent Application No.
2014-162904 filed on Aug. 8, 2014 including the specification,
drawings and abstract is incorporated herein by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to chain continuously variable
transmissions.
[0004] 2. Description of the Related Art
[0005] Continuously variable transmissions (CVTs) are known in
which two pulleys each have opposing conical surfaces and each are
configured so that the distance between the conical surfaces can be
changed, and a flexible endless member is wound around the two
pulleys. Rotation of one of the pulleys is transmitted to the other
pulley via the flexible endless member. At this time, the running
radius of the flexible endless member around each pulley is changed
by changing the distance between the opposing conical surfaces,
whereby the change gear ratio can be changed.
[0006] CVTs using a chain as the flexible endless member are known
in the art. In this chain, plate-like links each having an opening
are arranged in the circumferential direction of the chain. The
chain is formed by coupling chain elements to each other. Each
chain element includes a link unit and two pins. The link unit is
formed by a plurality of the links arranged in the lateral
direction of the chain The pins extend through both ends of each of
the openings of the links. The chain elements are coupled to each
other by inserting the pin of each chain element through the
openings of the links of another adjoining chain element.
[0007] Both ends of both or one of the two pins of each link unit
contact the opposing conical surfaces of the pulley. European
Patent Application Publication No. 1862700 (EP 1862700) discloses a
chain in which a contact point of a pin with a conical surface of a
pulley is located outside the centerline of the pin in the
thickness direction of the chain (see FIG. 3B). EP 1862700
describes that positioning the contact point in this manner can
reduce noise (see FIG. 5).
[0008] Loss that is caused by slipping at the contact point of the
pin with the pulley has not been considered in the chain CVTs.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to reduce loss that
is caused by slipping at a contact point of a pin with a
pulley.
[0010] According to one aspect of the present invention, a
continuously variable transmission includes: two pulleys each
having opposing conical surfaces and configured so that a distance
between the conical surfaces can be changed; and a chain that is
wound around the two pulleys and is held between the conical
surfaces. The continuously variable transmission is characterized
in that the chain includes plate-like links each having an opening
and arranged in a circumferential direction of the chain and is
formed by coupling chain elements to each other in the
circumferential direction of the chain, and each of the chain
elements includes a link unit that is formed by a plurality of the
links arranged in a lateral direction of the chain, and two pins
that extend through both ends of each of the openings of the links
and that contact the conical surfaces at their both ends. The chain
elements are coupled to each other by inserting the pin of each
chain element through the openings of the links of another chain
element adjoining in the circumferential direction of the chain. A
tensile force that is applied to the chain is transmitted between
the pins of the adjoining chain elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The foregoing and further features and advantages of the
invention will become apparent from the following description of
example embodiments with reference to the accompanying drawings,
wherein like numerals are used to represent like elements and
wherein:
[0012] FIG. 1 is a diagram showing a main part of a chain CVT;
[0013] FIG. 2 is a side view showing the structure of a chain;
[0014] FIG. 3 is a perspective view illustrating the structure of
the chain;
[0015] FIG. 4 is a plan view showing the structure of the
chain;
[0016] FIG. 5 is a diagram illustrating behavior of pins at the
time the chain is stretched and bent;
[0017] FIG. 6 is a diagram illustrating the behavior of the pins at
the time the chain is stretched and bent;
[0018] FIG. 7 is a graph showing the relation between the contact
point slip distance and the efficiency;
[0019] FIG. 8 is a graph showing the relation between the contact
point slip distance and the efficiency;
[0020] FIG. 9 is a graph showing the relation between the contact
point slip distance and the efficiency;
[0021] FIG. 10 is a diagram showing a coordinate system and a
parameter for chains of Specifications 1 and 2;
[0022] FIG. 11 is a diagram showing the coordinate system and
parameters for the chains of Specifications 1 and 2;
[0023] FIG. 12 is a graph showing the relation between the running
radius of the chain and the offset that minimizes the contact point
slip distance in the chain of Specifications 1;
[0024] FIG. 13 is a graph showing the relation between the running
radius of the chain and the minimum contact point slip distance in
the chain of Specifications 1;
[0025] FIG. 14 is a graph showing the relation of the offset and
the change gear ratio to the total contact point slip distance in
the chain of Specifications 1;
[0026] FIG. 15 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 0.417 in the chain of Specification 1;
[0027] FIG. 16 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 0.714 in the chain of Specification 1;
[0028] FIG. 17 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 1.000 in the chain of Specification 1;
[0029] FIG. 18 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 1.600 in the chain of Specification 1;
[0030] FIG. 19 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 2.400 in the chain of Specification 1;
[0031] FIG. 20 is an illustration of the pitch at the time the
chain is wound around a pulley;
[0032] FIG. 21 is a graph showing the relation between the running
radius of the chain and the offset that minimizes the contact point
slip distance in the chain of Specifications 2;
[0033] FIG. 22 is a graph showing the relation between the running
radius of the chain and the minimum contact point slip distance in
the chain of Specifications 2;
[0034] FIG. 23 is a graph showing the relation of the offset and
the change gear ratio to the total contact point slip distance in
the chain of Specifications 2;
[0035] FIG. 24 is a diagram showing a coordinate system and
parameters for a chain of Specifications 3;
[0036] FIG. 25 is a graph showing the relation between the running
radius of the chain and the offset that minimizes the contact point
slip distance in the chain of Specifications 3;
[0037] FIG. 26 is a graph showing the relation between the running
radius of the chain and the minimum contact point slip distance in
the chain of Specifications 3;
[0038] FIG. 27 is a graph showing the relation of the offset and
the change gear ratio to the total contact point slip distance in
the chain of Specifications 3;
[0039] FIG. 28 is a diagram showing a coordinate system and
parameters for a chain of Specifications 4;
[0040] FIG. 29 is a graph showing the relation between the running
radius of the chain and the offset that minimizes the contact point
slip distance in the chain of Specifications 4;
[0041] FIG. 30 is a graph showing the relation between the running
radius of the chain and the minimum contact point slip distance in
the chain of Specifications 4;
[0042] FIG. 31 is a graph showing the relation of the offset and
the change gear ratio to the total contact point slip distance in
the chain of Specifications 4;
[0043] FIG. 32 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 0.417 in the chain of Specifications 4;
[0044] FIG. 33 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 0.714 in the chain of Specifications 4;
[0045] FIG. 34 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 1.000 in the chain of Specifications 4;
[0046] FIG. 35 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 1.600 in the chain of Specifications 4; and
[0047] FIG. 36 is a graph showing the relation between the offset
and the total contact point slip distance for the change gear ratio
of 2.400 in the chain of Specifications 4.
DETAILED DESCRIPTION OF EMBODIMENTS
[0048] An embodiment of the present invention will be described
below with reference to the accompanying drawings. FIG. 1 shows a
main part of a chain CVT 10. The chain CVT 10 includes two pulleys
12, 14 and a chain 16 wound around the pulleys 12, 14. One of the
two pulleys is herein referred to as the "input pulley 12," and the
other pulley as the "output pulley 14." The input pulley 12 has a
fixed sheave 20 and a movable sheave 22. The fixed sheave 20 is
fixed to an input shaft 18. The movable sheave 22 can slide and
move along an input axis on the input shaft 18. The opposing
surfaces of the fixed and movable sheaves 20, 22 are shaped like
the side of a cone. These surfaces are herein referred to as the
"conical surfaces 24, 26." These conical surfaces 24, 26 form a
V-shaped groove, and the chain 16 is placed in this groove, namely
is interposed between the conical surfaces 24, 26, such that the
conical surfaces 24, 26 face the sides of the chain 16. Like the
input pulley 12, the output pulley 14 also has a fixed sheave 30
and a movable sheave 32. The fixed sheave 30 is fixed to an output
shaft 28. The movable sheave 32 can slide and move along an output
axis on the output shaft 28. The opposing surfaces of the fixed and
movable sheaves 30, 32 are shaped like the side of a cone. These
surfaces are herein referred to as the "conical surfaces 34, 36."
These conical surfaces 34, 36 form a V-shaped groove, and the chain
16 is placed in this groove, namely is interposed between the
conical surfaces 34, 36, such that the conical surfaces 34, 36 face
the sides of the chain 16.
[0049] The fixed sheave and the movable sheave are disposed in
reverse order between the input pulley 12 and the output pulley 14.
That is, the movable sheave 22 of the input pulley 12 is located on
the right side in FIG. 1, whereas the movable sheave 32 of the
output pulley 14 is located on the left side in FIG. 1. As the
movable sheave 22, 32 slides, the distance between the opposing
conical surfaces 24, 26 or between the opposing conical surfaces
34, 36 changes, and the width of the V-shaped groove formed by
these opposing conical surfaces 24, 26 or 34, 36 changes
accordingly. As the width of the V-shaped groove changes, the
running radius of the chain 16 around the pulley 12, 14 changes
accordingly. That is, as the movable sheave 22, 32 moves away from
the fixed sheave 20, 30, the width of the V-shaped groove increases
accordingly. The chain 16 thus moves to a deeper position in the
V-shaped groove, whereby the running radius decreases accordingly.
On the other hand, as the movable sheave 22, 32 moves toward the
fixed sheave 20, 30, the width of the V-shaped groove decreases
accordingly. The chain 16 thus moves to a shallower position in the
V-shaped groove, whereby the running radius increases accordingly.
The running radius is changed in the opposite directions between
the input pulley 12 and the output pulley 14 so that the chain 16
does not become slack. Since the movable sheave 22, 32 slides, the
width of the V-shaped groove changes continuously, and the running
radius also changes continuously. The change gear ratio in
transmission from the input shaft 18 to the output shaft 28 can
thus be changed continuously.
[0050] FIGS. 2 to 4 are views specifically showing the structure of
the chain 16. In the following description, the "circumferential
direction" refers to the direction along the direction in which the
chain 16 extends, the "lateral direction" refers to the direction
perpendicular to the circumferential direction and parallel to the
input shaft 18 and the output shaft 28, and the "thickness
direction" refers to the direction perpendicular to the
circumferential direction and the lateral direction. FIG. 2 is a
view showing a part of the chain 16 as viewed in the lateral
direction, FIG. 3 is a partial exploded view of the chain 16, and
FIG. 4 is a view showing the outer periphery of a part of the chain
16 as viewed in the thickness direction.
[0051] The horizontal direction in FIG. 2 corresponds to the
circumferential direction, and the vertical direction in FIG. 2
corresponds to the thickness direction. The chain 16 is formed by
combining plate-like links 40 each having an opening 38 and
bar-like pins 42a, 42b. The links 40 have the same shape and the
same thickness, and the bar-like pins 42a, 42b have the same shape.
The links 40 are arranged in a predetermined pattern in the lateral
direction (see FIG. 4). Two pins 42a, 42b extend through both ends
of the opening 38 of each link 40. Both ends of the two pins 42a,
42b or both ends of one of the two pins 42a, 42b contact the
conical surfaces 24, 26, 34, 36 of the input and output pulleys 12,
14. Each set of the two pins 42a, 42b and those links 40 having the
two pins 42a, 42b extending therethrough is herein referred to as
the "chain element 44." FIG. 3 shows two chain elements 44-1, 44-2.
The characters "-1," "-2," and "-3" are added for distinguishing
each chain element and its links and pins from the other chain
elements. The chain element 44-1 is formed by a plurality of links
40-1 and two pins 42a-1, 42b-1 extending through the links 40-1.
The two pins 42a-1, 42b-1 are press-fitted or fixedly positioned in
both ends of an opening 38-1 of the link 40-1, whereby the two pins
42a-1, 42b-1 are coupled to the link 40-1. Similarly, the chain
element 44-2 is formed by a plurality of links 40-2 and two pins
42a-2, 42b-2 extending through the links 40-2. Those links 40
forming a single chain element 44 are herein collectively referred
to as the "link unit 46." The characters "-1," "-2," and "-3" are
added when identifying the chain element including the link unit
46.
[0052] The adjoining chain elements 44-1, 44-2 are coupled together
by inserting the pins 42a, 42b through the openings 38 of each
other's links 40. As shown in FIG. 3, the pin 42b-1 of the left
chain element 44-1 is inserted into the opening 38-2 so as to be
located on the right side of the pin 42a-2 of the right chain
element 44-2. The pin 42a-2 of the right chain element 44-2 is
inserted into the opening 38-1 so as to be located on the left side
of the pin 42b-1 of the left chain element 44-1. These two pins
42b-1, 42a-2 engage with each other, so that a tensile force of the
chain 16 is transmitted therebetween. When the chain 16 is bent,
adjoining pins, e.g., the pins 42b-1, 42a-2, move so as to roll on
each other's contact surfaces. The chain 16 is thus allowed to be
bent.
[0053] FIG. 4 shows the links 40 and the pins 42a, 42b of three
chain elements 44. Those chain elements 44 adjoining these three
chain elements 44 are not shown in FIG. 4. A plurality of links 40
are arranged in the lateral direction (the horizontal direction in
FIG. 4) and are shifted as appropriate in the circumferential
direction. The chain elements 44 are thus connected in the
circumferential direction to form a single chain. The arrangement
of the links 40 shown in the figure is by way of example only, and
the links 40 may be arranged in other patterns.
[0054] FIGS. 5 and 6 show behavior of the chain 16, especially the
pins 42a, 42b, at the time the chain 16 engages with one of the
pulleys 12, 14. For simplicity, the behavior of the chain 16 will
be described below with respect to the input pulley 12. FIGS. 5 and
6 show the state of the chain 16 as viewed from a fixed point on
the input pulley 12. FIG. 5 shows the state where the link 40-3 has
started to engage with the input pulley 12, and FIG. 6 shows the
state where the link 40-3 has completely engaged with the input
pulley 12. In FIGS. 5 and 6, black circles " " and white circles
".largecircle." represent contact points 48 of the pins 42a, 42b
with the conical surface of the input pulley 12 at the time the
pins 42a, 42b are interposed between the conical surfaces of the
input pulley 12 (hereinafter these contact points are referred to
as the "pin-pulley contact points 48"). Each black circle shows the
pin-pulley contact point 48 at the time the chain element 44
including a corresponding pin has completely engaged with the input
pulley 12. In FIG. 5, the chain element 44-1 has completely engaged
with the input pulley 12. The pin-pulley contact points 48 of the
two pins 42a-1, 42b-1 of this chain element 44-1 are therefore
shown by the black circles. Each white circle shows the pin-pulley
contact point 48 at the time the chain element 44 including a
corresponding pin has not completely engaged with the input pulley
12. The pins do not contact the pulley before entering the V-shaped
groove of the pulley. However, for convenience of description, the
pin-pulley contact points as used herein include those points that
are going to contact the pulley.
[0055] In FIGS. 5 and 6, double circles represent contact points 50
between the pins (hereinafter these contact points are referred to
as the "pin-pin contact points 50"). The pin-pin contact points 50
move as the chain 16 is wound around the input pulley 12. The
pin-pin contact point 50A in FIGS. 5 and 6 shows the pin-pin
contact point at the time a corresponding chain element 44 of the
chain 16 has started to be wound around the input pulley 12 (FIG.
5) and at the time the corresponding chain element 44 of the chain
16 has been completely wound around the input pulley 12 (FIG. 6).
As the pin 42b-3 of the chain element 44-3 moves so as to roll on
the side surface of the pin 42a-1, the pin-pin contact point 50A
moves outward in the thickness direction of the chain 16. The
pin-pin contact point 50A moves until the chain element 44-3
completely engages with the input pulley 12.
[0056] Contact between the pins and contact between the pin and the
pulley are actually surface contact rather than point contact due
to deformation of the members. However, deformation of the members
such as the pins and the pulley is herein not considered, and it is
herein assumed that the pins and the pulley are completely rigid
and point-contact each other.
[0057] Each of the pin-pulley contact points 48 is a fixed point on
the end face of the pin 42. However, the pin-pulley contact points
48 move on the conical surface of the input pulley 12 as the chain
16 is wound around the input pulley 12. In FIG. 5, the chain
element 44-3 has started to be wound around the input pulley 12. At
this time, the pin-pulley contact point 48A of the front one 42b-3
of the two pins of the chain element 44-3 is located inside an arc
(shown by a dashed line in the figure) passing through the
pin-pulley contact points 48 shown by the black circles on the
conical surface of the input pulley 12. The pin-pulley contact
point 48A moves outward in the radial direction of the input pulley
12 as the chain element 44-3 is wound around the input pulley 12.
The pin-pulley contact point 48A reaches the arc shown by the
dashed line when the rear pin 42a-3 is held between the conical
surfaces of the input pulley 12, namely when the chain element 44-3
has been completely wound around the input pulley 12. The
pin-pulley contact point 48A thus moves on the conical surface of
the input pulley 12 as the chain element 44-3 is wound around the
input pulley 12. Friction that is generated by slipping between the
pin-pulley contact point 48A and the conical surface of the input
pulley 12 contributes to loss of the chain CVT. Similarly, the
pin-pulley contact point 48 slips on the conical surface of the
output pulley 14 when the chain 16 is wound around the output
pulley 14.
[0058] The pin-pulley contact points 48 also slip when the chain 16
leaves the pulley 12, 14. At this time, the pin-pulley contact
point 48 of the rear pin 42 of the chain element 44 that is leaving
the pulley 12, 14 moves on the conical surface of the pulley 12,
14.
[0059] As described above, when the chain 16 enters and leaves the
pulley 12, 14, that is, when the chain 16 is stretched and bent to
be changed between a bent state and a linear state, the pin-pulley
contact points 48 slip and move on the conical surface of the
pulley 12, 14. The distance by which the pin-pulley contact points
48 move in the thickness direction of the chain 16 at this time is
hereinafter referred to as the "contact point slip distance S." The
larger the contact point slip distance S is, the greater the loss
is. The contact point slip distance S is larger in the case where
the chain 16 is bent to a larger extent, that is, in the case where
the running radius of the chain 16 is smaller. In the chain CVT 10,
the running radius of the chain 16 is different between the input
pulley 12 and the output pulley 14 except in the case where the
change gear ratio is 1. Accordingly, the contact point slip
distance S is also different between the input pulley 12 and the
output pulley 14 except in the case where the change gear ratio is
1. Friction loss between the chain 16 and the pulley 12, 14
therefore needs to be evaluated for the sum of the contact point
slip distances S between the two pins 42a, 42b and the pulley 12,
14 at the time a single chain element 44 moves around the pulleys
12, 14. The sum of the contact point slip distances S is herein
referred to as the "total contact point slip distance T."
[0060] FIGS. 7 to 9 are graphs with the abscissa representing the
total contact point slip distance T and the ordinate representing
efficiency. Plotted points in each figure show the result for
chains having different specifications. Specifically, the plotted
points in each figure show the result for chains that are different
in the shape of the contact surface between the pins (the shape of
an action curve described below) and in the positions of the
pin-pin contact points and the positions of the pin-pulley contact
points in the chain in the linear state. FIGS. 5 and 6 show an
example in which two pins of each chain element 44 contact the
pulley. However, FIGS. 7 to 9 also show an example in which only
one of the two pins of each chain element 44 contacts the pulley.
FIGS. 7 to 9 show the cases where the change gear ratio is 0.5,
0.7, and 1.0, respectively. The result of FIGS. 7 to 9 shows that
the shorter the total contact point slip distance T is, the higher
the efficiency is.
[0061] The shape of the pins which reduces the contact point slip
distance S will be described below. For illustration, a coordinate
system and parameters are defined as shown in FIGS. 10 and 11. FIG.
10 shows the chain 16 in the linear state. The pin-pin contact
point 50 of the chain 16 in the linear state is the origin of the
coordinate axes. The x-axis is the circumferential direction of the
chain 16, and the positive direction of the x-axis is the traveling
direction of the chain 16. The y-axis is the thickness direction of
the chain 16, and the positive direction of the y-axis is the
radially outward direction of the chain 16. The z-axis is the
lateral direction of the chain 16. That is, the z-axis is an axis
perpendicular to the x-axis and the y-axis. The positive direction
of the z-axis is determined so as to create a right-handed
coordinate system. The distance between adjoining pin-pin contact
points 50 is herein referred to as the "contact point pitch P."
Since the pin-pin contact points 50 move as the chain 16 is bent,
the contact point pitch P varies depending on the bent state of the
chain 16.
[0062] FIG. 11 is a diagram showing only two of the pins 42a, 42b
which contact each other. The pins have the same sectional shape
along the z-direction except their both ends. The end faces of each
pin are tilted according to the conical surfaces of the pulleys 12,
14. The sectional shape of each pin therefore varies in the regions
including the end faces thereof. For simplicity, the shape of the
pins 42a, 42b will be described by using a projection on a plane
perpendicular to the z-axis. The pin-pin contact point 50 actually
appears as a line extending parallel to the z-axis. Those parts of
the opposing side surfaces of the two pins 42a, 42b which are
located on the positive side of the y-axis are herein referred to
as the "action curve 52." When distinguishing between the action
curves 52 of the two pins 42a, 42b, the action curve of the pin 42a
is referred to as the "action curve 52a," and the action curve of
the pin 42b is referred to as the "action curve 52b." In the
following description, when it is necessary to distinguish the
elements relating to the pin 42a from those relating to the pin
42b, the letter "a" is added to the reference characters denoting
the elements relating to the pin 42a, and the letter "b" is added
to the reference characters denoting the elements relating to the
pin 42b. When the chain 16 is stretched and bent, the pin-pin
contact point 50 moves on the action curves 52.
[0063] The end faces of the pins 42a, 42b are curved outward in a
convex shape. The sections of the pins 42a, 42b perpendicular to
the y-axis are curved in a convex shape toward the conical surfaces
of the pulley 12, 14. For each of the pins 42a, 42b, the line
connecting the outermost points of the end face of the pin 42a, 42b
in each section of the pin 42a, 42b perpendicular to the y-axis is
herein referred to as the "end face ridge." The end face ridge
projected on an x-y plane is referred to as the "projected ridge
54," The length of the projected ridge 54 is referred to as the
"projected ridge length L." When distinguishing between the
projected ridges of the two pins 42a, 42b, the projected ridge of
the pin 42a is referred to as the "projected ridge 54a," and the
length thereof is referred to as the "projected ridge length La."
The projected ridge of the pin 42b is referred to as the "projected
ridge 54b," and the length thereof is referred to as the "projected
ridge length Lb." The inclination of the projected ridge 54 (54a,
54b) with respect to the y-axis is denoted by "a (aa, ab)." The
distance between the intersection of the projected ridge 54 (54a,
54b) with the x-axis and the origin is denoted by "d (da, db)." The
midpoint of the projected ridge 54 (54a, 54b) is referred to as the
"pin center C (Ca, Cb)." The distance of the pin-pulley contact
point 48 from the x-axis, namely the y-coordinate of the pin-pulley
contact point 48, is referred to as the "offset h." In other words,
the offset h is a directed distance of the pin-pulley contact point
48 from the pin-pin contact point 50 as a reference point in the
thickness direction of the chain 16. The positive direction of the
y-axis is the positive direction of the offset h or the directed
distance.
[0064] Table 1 shows specific values of the parameters described
above in the embodiment of the chain 16, specifically the pins 42.
These values are hereinafter referred to as "Specifications 1." In
this example, the two pins 42a, 42b have the same shape, and as
shown in FIGS. 10 and 11, the sectional shapes of the two pins 42a,
42b are mirror images of each other with respect to the y-axis.
Accordingly, behavior of the pin 42b at the time the chain element
44 enters the pulley 12, 14 is symmetrical to that of the pin 42a
at the time the chain element 44 leaves the pulley 12, 14, and the
contact point slip distance S is the same between the pins 42a,
42b. Only one of the pins 42a, 42b will therefore be described
below. The action curves 52 of the pins 42a, 42b are arcs
tangential to each other at the origin and having a radius of 9.5
mm The chain 16 of the present embodiment is an endless chain
having 90 chain elements connected together.
TABLE-US-00001 TABLE 1 [Specifications 1] Contact with pulley Two
pins contact pulley Pin shape Two pins have the same shape Action
curve Arc with radius of 9.5 mm Contact point pitch P (in linear
state) 7.14 mm Inclination .alpha. of projected ridge 8.5.degree.
Projected ridge length L 5.9 mm Distance d of projected ridge from
origin 1.466 mm Total number of chain elements 90 y-coordinate of
pin center C 0.874 mm Shaft distance 156 mm
[0065] FIG. 12 is a graph showing the offset h that minimizes the
contact point slip distance S for each running radius of the chain
16 of Specifications 1 described in Table 1. Since the pin 42
contacts the conical surfaces of the pulley 12, 14, the position of
the pin-pulley contact point 48 on the pin 42a, 42b does not change
even if the running radius changes. As can be seen from FIG. 12,
the offset h that minimizes the contact point slip distance S
monotonically decreases with an increase in running radius.
Accordingly, if the offset h is set in the range corresponding to
the shift range that can be attained by the chain CVT, namely in
the range of offset corresponding to the running radius range, the
contact point slip distance S is minimized when the chain CVT is
operated with the corresponding running radius in the running
radius range. In particular, it is preferable to set the offset h
to a value corresponding to the running radius of the change gear
ratio that is frequently used. Reducing the contact point slip
distance S is also advantageous in terms of friction.
[0066] For example, the offset h can be set as follows in the case
of using the running radius of 30 to 73 mm. The offset h that
minimizes the contact point slip distance S is 0.340 mm when the
running radius is 30 mm, and is 0.0126 mm when the running radius
is 73 mm. Setting the offset h between 0.0126 mm and 0.340 mm, both
inclusive, can minimize the contact point slip distance S at a
running radius of the corresponding change gear ratio in the shift
range and can thus reduce slip loss.
0.0126 mm.ltoreq.h.ltoreq.0.340 mm (1)
[0067] FIG. 13 is a graph showing the relation between the running
radius and the minimum contact point slip distance S. The offset h
that minimizes the contact point slip distance S is obtained for
each running radius, and the minimum contact point slip distance S
for each running radius is shown in the graph. The graph shows that
the contact point slip distance S increases as the running radius
decreases, namely as the chain 16 is bent to a larger extent.
[0068] FIG. 14 is a graph showing the relation of the change gear
ratio and the offset h to the total contact point slip distance T.
The abscissa represents the offset h, and the ordinate represents
the change gear ratio. Lines that look like contour lines are lines
connecting the same total contact point slip distances T. The
closer the offset h is to zero, that is, the closer the pin-pulley
contact point 48 is to the origin, the smaller the total contact
point slip distance T is. Accordingly, setting the offset h in a
certain range close to the origin can reduce the total contact
point slip distance T in the shift range. For the change gear ratio
of 1.0 (running radius: 51.5 mm), the total contact point slip
distance T is minimized when the offset h is 0.102 mm.
[0069] FIGS. 15 to 19 are graphs showing the relation between the
offset and the total contact point slip distance T at certain
change gear ratios. FIG. 15 is a graph for the change gear ratio of
0.417, FIG. 16 is a graph for the change gear ratio of 0.714, FIG.
17 is a graph for the change gear ratio of 1.000, FIG. 18 is a
graph for the change gear ratio of 1.600, and FIG. 19 is a graph
for the change gear ratio of 2.400. These graphs can be regarded as
sectional views of FIG. 14 taken along these change gear ratios.
These graphs also show that there is a range close to the origin
where the total contact point slip distance T is small. In FIGS. 15
to 19, the lower 30% of the range between the minimum and maximum
total contact point slip distances T at each change gear ratio is
shown by a dashed line. For example, in FIG. 15, the maximum value
of the total contact point slip distance T is 2.097 mm, the minimum
value thereof is 1.031 mm, and the lower 30% line of the range
between the minimum and maximum values is 1.351 mm. When the offset
h is in the range of -0.5 mm to 0.5 mm, the total contact point
slip distance T is 1.134 mm or less. Namely, the total contact
point slip distance T is in the lower 30% range. In FIGS. 16 to 19
as well, when the offset h is in the range of -0.5 mm to 0.5 mm,
the total contact point slip distance T is in the lower 30% range.
These graphs show that setting the offset h in the range of -0.5 mm
to 0.5 mm allows the chain CVT to be operated with the total
contact point slip distance T being small in the entire range of
the change gear ratio to be actually used. The value of 0.5 mm is
0.085 times the projected ridge length L (5.9 mm). Setting the
absolute value of the offset h to a value equal to or smaller than
0.085 times the projected ridge length L thus allows the chain CVT
to be operated with the total contact point slip distance T being
small in the entire shift range.
-0.085.times.L mm.ltoreq.h.ltoreq.0.085.times.L mm (2)
[0070] In the above description, the offset h is set in view of the
slip loss, namely the efficiency. However, noise needs to be also
considered to set the offset h. In the chain CVT, impact that
occurs when the pins engage with the pulley contributes noise. In
the case where the chain 16 is accelerated when a chord region of
the chain 16 enters the pulley 12, 14, impact that occurs when the
chain 16 hits the pulley 12, 14 is increased. It is therefore
desired that the pins not be accelerated when entering the pulley
12, 14.
[0071] FIG. 20 is a diagram schematically showing the state where
the chain 16 is wound around the pulley 12, 14, and shows the
pin-pin contact points 50. In the figure, ".theta." represents an
angle formed between lines drawn from the center of the pulley 12,
14 to both ends of an arc drawn between adjoining pin-pin contact
points 50, namely an angle formed between lines drawn from the
center of the pulley 12, 14 to adjoining pin-pin contact points 50,
and "R(.theta.)" represents the distance between the pin-pin
contact point 50 and the center of the pulley 12, 14 (running
radius). The relation between the distance (pitch) pitch(.theta.)
between adjoining pin-pin contact points 50 and the running radius
R(.theta.) is given by the following expression (3).
R ( .theta. ) = pitch ( .theta. ) 2 sin ( .theta. 2 ) ( 3 )
##EQU00001##
[0072] If the pitch pitch(.theta.) at the time the chain 16 is
wound around the pulley 12, 14 is equal to or larger than the
contact point pitch P (7.14 mm) at the time the chain 16 is in the
linear state, the pins 42a, 42b are not accelerated when entering
the pulley 12, 14. In Specifications 1, the offset h that satisfies
the above conditions even at the minimum running radius is 0.346 mm
or more.
0.346 mm.ltoreq.h (4)
[0073] The range of the offset h which is obtained based on the
offsets h that minimize the contact point slip distance S at the
maximum running radius and the minimum running radius, namely
0.0126 mm.ltoreq.h.ltoreq.0.340 mm (Expression (1)), and the range
of the offset h which is obtained in view of noise, namely 0.346
mm.ltoreq.h (Expression (4)), do not overlap each other.
Accordingly, in the case where anti-noise measures are prioritized,
the offset h is set to 0.346 mm that is as close as possible to the
range obtained based on the offsets h that minimize the contact
point slip distance S at the maximum running radius and the minimum
running radius.
h=0.346 mm (5)
[0074] In view of both the range of the offset h which is obtained
so that the chain CVT is operated in the range where the total
contact point slip distance T is small, namely -0.085.times.L
mm.ltoreq.h.ltoreq.0.085.times.L mm (Expression (2)), and the range
of the offset h which is obtained in view of noise, namely 0.346
mm.ltoreq.h (Expression (4)), setting the offset h between 0.346 mm
and 0.085.times.L mm, both inclusive, can reduce slip loss and
noise.
0.346 mm.ltoreq.h.ltoreq.0.085.times.L mm (6)
[0075] It is described above that the offset h is the same between
the two pins 42a, 42b. However, the offset h may be different
between the two pins 42a, 42b. That is, the offsets ha, hb of the
two pins 42a, 42b may be set to different values in the range shown
by Expressions (1), (2), and (6).
[0076] A chain of Specifications 2 shown in Table 2 will be
described below. Specifications 2 are different from Specifications
1 in that the pin-pin contact point 50 (origin) of the chain 16 in
the linear state is closer to the midpoint C of the projected ridge
54.
TABLE-US-00002 TABLE 2 [Specifications 2] Contact with pulley Two
pins contact pulley Pin shape Two pins have the same shape Action
curve Arc with radius of 9.5 mm Contact point pitch P (in linear
state) 7.14 mm Inclination .alpha. of projected ridge 8.5.degree.
Projected ridge length L 5.9 mm Distance d of projected ridge from
origin 1.502 mm Total number of chain elements 90 y-coordinate of
pin center C 0.164 mm Shaft distance 156 mm
[0077] FIG. 21 is a graph showing the offset h that minimizes the
contact point slip distance S for each running radius of the chain
16 of Specifications 2. In Specifications 2, the pin shape is the
same as in Specifications 1. The offset h that minimizes the
contact point slip distance S is the same as in Specifications 1.
That is, setting the offset h of the two pins between 0.0126 mm and
0.340 mm, both inclusive, can minimize the contact point slip
distance S at the corresponding running radius.
0.0126 mm.ltoreq.h.ltoreq.0.340 mm (7)
[0078] FIG. 22 is a graph showing the relation between the running
radius and the minimum contact point slip distance S in the chain
16 of Specifications 2. The distance d of the projected ridge 54
from the origin is slightly larger in Specifications 2 than in
Specifications 1. Accordingly, the minimum contact point slip
distance per pin is slightly longer in FIG. 22, namely in
Specifications 2, than in FIG. 13.
[0079] FIG. 23 is a graph showing the relation of the change gear
ratio and the offset h to the total contact point slip distance T
in Specifications 2. The abscissa represents the offset h, and the
ordinate represents the change gear ratio. Lines that look like
contour lines are lines connecting the same total contact point
slip distances T. As in Specifications 1 (FIG. 14), the closer the
offset h is to zero, that is, the closer the pin-pulley contact
point 48 is to the origin, the smaller the total contact point slip
distance T is. In Specifications 2, for the change gear ratio of
1.0, the total contact point slip distance T is minimized when the
offset h is 0.094 mm.
[0080] In FIGS. 14 and 23, the range of the abscissa shows the
range of the projected ridge 54. Namely, the position on the
abscissa represents the position on the projected ridge 54. FIGS.
14 and 23 are different from each other in the position of the
origin, i.e., the pin-pin contact point 50 at the time the chain 16
is in the linear state, on the projected ridge 54. In FIG. 23, the
origin is located near the midpoint of the projected ridge 54. The
graph of FIG. 23 is similar to the graph of FIG. 14 shifted to the
right according to the shift of the origin. This shows that a
factor that reduces the contact point slip distance S is not where
to position the pin-pulley contact point 48 on the projected ridge
54 but positioning the pin-pulley contact point 48 near the pin-pin
contact point 50 (origin). Accordingly, setting the offset h in the
same range as in the example of Specifications 1 (between
.about.0.085.times.L mm and 0.085.times.L mm, both inclusive)
allows the chain CVT to be operated with the total contact point
slip distance T being small in the entire shift range.
-0.085.times.L mm.ltoreq.h.ltoreq.0.085.times.L mm (8)
[0081] In the case where noise is considered, Expression (3) is
used to obtain the condition that the pin is not accelerated when
entering the pulley 12, 14. In Specifications 2, the offset h needs
to be 0.340 mm or more.
0.340 mm.ltoreq.h (9)
[0082] The range of the offset h which is obtained based on the
offsets h that minimize the contact point slip distance S at the
maximum running radius and the minimum running radius, namely
0.0126 mm.ltoreq.h.ltoreq.0.340 mm (Expression (7)), and the range
of the offset h which is obtained in view of noise, namely 0.340
mm.ltoreq.h (Expression (9)), overlap each other at 0.340 mm, and
the offset h is set to this value.
h=0.340 mm (10)
[0083] In view of both the range of the offset h which is obtained
so that the chain CVT is operated in the range where the total
contact point slip distance T is small, namely -0.085.times.L
mm.ltoreq.h.ltoreq.0.085.times.L mm (Expression (8)), and the range
of the offset h which is obtained in view of noise, namely 0.340 mm
h (Expression (9)), setting the offset h between 0.340 mm and
0.085.times.L mm, both inclusive, can reduce slip loss and
noise.
0.340 mm.ltoreq.h.ltoreq.0.085.times.L mm (11)
[0084] It is described above that the offset h in Specifications 1
and 2 is the same between the two pins 42a, 42b. However, the
offset h may be different between the two pins 42a, 42b. That is,
the offsets ha, hb of the two pins 42a, 42b may be set to different
values in the range shown by Expressions (7), (8), and (11).
[0085] A chain of Specifications 3 shown in Table 3 will be
described below.
TABLE-US-00003 TABLE 3 [Specifications 3] Contact with pulley Only
pin 42a contacts pulley Pin shape Two pins have different shapes
Action curve of pin 42a Involute curve with base circle radius of
52 mm Action curve of pin 42b Straight line parallel to y-axis
Contact point pitch P (in linear state) 7.14 mm Inclination
.alpha.a of projected ridge of pin 42a 8.5.degree. Projected ridge
length La of pin 42a 5.9 mm Distance da of projected ridge of pin
42a 1.466 mm from origin Total number of chain elements 90
y-coordinate of center Ca of pin 42a 0.874 mm Shaft distance 156
mm
[0086] Specifications 3 is an example in which the two pins 42a,
42b have different shapes, and only one of the pins 42a, 42b,
namely only the pin 42a, contacts the pulley 12, 14. Accordingly,
only slipping of the pin 42a on the pulley 12, 14 needs to be
considered. FIG. 24 shows the positional relation between the pins
42a, 42b of the chain 16 in the linear state. A coordinate system
is defined similarly to FIGS. 10 and 11. The pin-pin contact point
50 of the chain 16 in the linear state is the origin of the
coordinate axes. The x-axis is the circumferential direction of the
chain 16, the y-axis is the thickness direction of the chain 16,
and the z-axis is the lateral direction of the chain 16. Parameters
such as the contact point pitch, action curves, projected ridges,
etc. are defined similarly to those described with respect to FIGS.
10 and 11. The action curve 52a of the pin 42a is an involute curve
having its origin at the pin-pin contact point 50 and having a base
circle radius of 52 mm. The action curve 52b of the pin 42b is a
straight line parallel to the y-axis.
[0087] FIG. 25 is a graph showing the offset h that minimizes the
contact point slip distance S for each running radius of the chain
16 of Specifications 3. The offset h is set as follows in the case
of using the running radius of 30 to 73 mm The offset h that
minimizes the contact point slip distance S is 0.275 mm when the
running radius is 30 mm, and is -0.135 mm when the running radius
is 73 mm. Setting the offset h between -0.135 mm and 0.275 mm, both
inclusive, can minimize the contact point slip distance S at the
corresponding running radius and can reduce slip loss.
-0.135 mm.ltoreq.h.ltoreq.0.275 mm (12)
[0088] FIG. 26 is a graph showing the relation between the running
radius and the minimum contact point slip distance S per pin. The
offset h that minimizes the contact point slip distance S is
obtained for each running radius, and the minimum contact point
slip distance S for each running radius is shown in the graph. The
graph shows that the contact point slip distance S increases as the
running radius decreases, namely as the chain 16 is bent to a
larger extent.
[0089] FIG. 27 is a graph showing the relation of the change gear
ratio and the offset h to the total contact point slip distance T.
The abscissa represents the offset h, and the ordinate represents
the change gear ratio. Lines that look like contour lines are lines
connecting the same total contact point slip distances T. The
closer the offset h is to zero, that is, the closer the pin-pulley
contact point 48 is to the origin, the smaller the total contact
point slip distance T is. Accordingly, setting the offset h in a
certain range close to the origin can reduce the total contact
point slip distance T in the shift range. For the change gear ratio
of 1.0 (running radius: 51.5 mm), the total contact point slip
distance T is minimized when the offset h is -0.056 mm.
[0090] In Specifications 3 as well, the offset h is set in the
range where the total contact point slip distance T is small,
namely in the lower 30% of the range between the minimum and
maximum total contact point slip distances T, as in the case of
Specifications 1 and 2. In this case as well, setting the absolute
value of the offset h to 0.5 mm or less (0.085.times.L or less)
thus allows the chain CVT to be operated in the range where the
total contact point slip distance T is small.
-0.085.times.L mm.ltoreq.h.ltoreq.0.085.times.L mm (13)
[0091] In the case where noise is considered in Specifications 3,
such an offset h that makes the pitch at the minimum running radius
equal to or larger than the contact point pitch P (7.14 mm) of the
chain 16 in the linear state is obtained similarly to
Specifications 1 and 2. This offset h is 0.279 mm or more.
0.279 mm.ltoreq.h (14)
[0092] The range of the offset h which is obtained based on the
offsets h that minimize the contact point slip distance S at the
maximum running radius and the minimum running radius, namely
-0.135 mm.ltoreq.h.ltoreq.0.275 mm (Expression (12)), and the range
of the offset h which is obtained in view of noise, namely 0.279
mm.ltoreq.h (Expression (14)), do not overlap each other.
Accordingly, in the case where anti-noise measures are prioritized,
the offset h is set to 0.279 mm that is as close as possible to the
range obtained based on the offsets h that minimize the contact
point slip distance S at the maximum running radius and the minimum
running radius.
h=0.279 mm (15)
[0093] In view of both the range of the offset h which is obtained
so that the chain CVT is operated in the range where the total
contact point slip distance T is small, namely -0.085.times.L
mm.ltoreq.h.ltoreq.0.085.times.L mm (Expression (13)), and the
range of the offset h which is obtained in view of noise, namely
0.279 mm.ltoreq.h (Expression (14)), setting the offset h between
0.279 mm and 0.085.times.L mm, both inclusive, can reduce slip loss
and noise.
0.279 mm.ltoreq.h.ltoreq.0.085.times.L mm (16)
[0094] A chain of Specifications 4 shown in Table 4 will be
described below.
TABLE-US-00004 TABLE 4 [Specifications 4] Contact with pulley Two
pins contact pulley Pin shape Two pins have different shapes Action
curve of pin 42a Involute curve with base circle radius of 52 mm
Action curve of pin 42b Straight line parallel to y-axis Contact
point pitch P (in linear state) 7.14 mm Inclination .alpha.a of
projected ridge of pin 42a 8.5.degree. Inclination .alpha.b of
projected ridge of pin 42b 0.degree. Projected ridge length La of
pin 42a 5.9 mm Projected ridge length Lb of pin 42b 5.9 mm Distance
da of projected ridge of pin 42a 1.466 mm from origin Distance db
of projected ridge of pin 42b 0.875 mm from origin Total number of
chain elements 90 y-coordinate of center Ca of pin 42a 0.874 mm
y-coordinate of center Cb of pin 42b 0.874 mm Shaft distance 156
mm
[0095] Specifications 4 is an example in which the two pins 42a,
42b have different shapes, and both pins 42a, 42b contact the
pulley 12, 14. FIG. 28 shows the positional relation between the
pins 42a, 42b of the chain 16 in the linear state. A coordinate
system is defined similarly to FIGS. 10 and 11. The pin-pin contact
point 50 of the chain 16 in the linear state is the origin of the
coordinate axes. The x-axis is the circumferential direction of the
chain 16, the y-axis is the thickness direction of the chain 16,
and the z-axis is the lateral direction of the chain 16. Parameters
such as the contact point pitch, action curves, projected ridges,
etc. are defined similarly to those described with respect to FIGS.
10 and 11. The action curve 52a of the pin 42a is an involute curve
having its origin at the pin-pin contact point 50 and having a base
circle radius of 52 mm. The action curve 52b of the pin 42b is a
straight line parallel to the y-axis.
[0096] FIG. 29 is a graph showing the offset h that minimizes the
contact point slip distance S for each running radius of the chain
16 of Specifications 4. Since the two pins 42a, 42b have different
shapes, the two pins 42a, 42b behave differently and the offsets
ha, hb of the two pins 42a, 42b which minimize the contact point
slip distance S are different from each other. The offsets ha, hb
are set as follows in the case of using the running radius of 30 to
73 mm The offset ha of the pin 42a which minimizes the contact
point slip distance S is 0.275 mm when the running radius is 30 mm,
and is -0.135 mm when the running radius is 73 mm. The offset hb of
the pin 42b which minimizes the contact point slip distance S is
0.498 mm when the running radius is 30 mm, and is 0.084 mm when the
running radius is 73 mm. In the case where the offsets ha, hb of
the two pins 42a, 42b are set to different values, the offset ha of
the pin 42a is set between -0.135 mm and 0.275 mm, both inclusive,
and the offset hb of the pin 42b is set between 0.084 mm and 0.498
mm, both inclusive. Setting the offsets ha, hb in this manner can
minimize the contact point slip distance S at the corresponding
running radius and can reduce slip loss.
-0.135 mm.ltoreq.ha.ltoreq.0.275 mm (17a)
0.084 mm.ltoreq.hb.ltoreq.0.498 mm (17b)
[0097] In the case of setting the offsets ha, hb of the two pins
42a, 42b to the same value, the offsets ha, hb are set between the
smaller one of the minimum values of the offsets ha, hb, namely
-0.135 mm, and the larger one of the maximum values of the offsets
ha, hb, namely 0.498 mm, both inclusive. Setting the offsets ha, hb
in this range can minimize the contact point slip distance S of one
of the pins 42a, 42b at the corresponding running radius and can
reduce slip loss.
-0.135 mm.ltoreq.ha.ltoreq.0.498 mm (18a)
-0.135 mm.ltoreq.hb.ltoreq.0.498 mm (18b)
[0098] In another example of setting the offsets ha, hb of the two
pins 42a, 42b to the same value, the offsets ha, hb may be set in
the common range of Expressions (17a), (17b), namely between 0.084
mm and 0.275 mm, both inclusive.
0.084 mm.ltoreq.ha.ltoreq.0.275 mm (19a)
0.084 mm.ltoreq.hb.ltoreq.0.275 mm (19b)
[0099] FIG. 30 is a graph showing the relation between the running
radius and the minimum contact point slip distance S per pin. Since
the two pins 42a, 42b have different shapes, the two pins 42a, 42b
behave differently and the minimum contact point slip distance S is
different between the two pins 42a, 42b. The offset h that
minimizes the contact point slip distance S is obtained for each
running radius, and the minimum contact point slip distance S for
each running radius is shown in the graph. The graph shows that the
contact point slip distance S increases as the running radius
decreases, namely as the chain 16 is bent to a larger extent.
[0100] FIG. 31 is a graph showing the relation of the change gear
ratio and the offset h to the total contact point slip distance T.
The abscissa represents the offset h, and the ordinate represents
the change gear ratio. Lines that look like contour lines are lines
connecting the same total contact point slip distances T. In this
example, a calculation is made on the assumption that the offsets
ha, hb of the two pins 42a, 42b are the same (ha, hb=h). The closer
the offset h is to zero, that is, the closer the pin-pulley contact
point 48 is to the origin, the smaller the total contact point slip
distance T is. Accordingly, setting the offset h in a certain range
close to the origin can reduce the total contact point slip
distance T in the shift range. For the change gear ratio of 1.0
(running radius: 51.5 mm), the total contact point slip distance T
is minimized when the offset h is 0.072 mm.
[0101] FIGS. 32 to 36 are graphs showing the relation between the
offset and the total contact point slip distance T at certain
change gear ratios, as in FIGS. 15 to 19. FIG. 32 is a graph for
the change gear ratio of 0.417, FIG. 33 is a graph for the change
gear ratio of 0.714, FIG. 34 is a graph for the change gear ratio
of 1.000, FIG. 35 is a graph for the change gear ratio of 1.600,
and FIG. 36 is a graph for the change gear ratio of 2.400. These
graphs can be regarded as sectional views of FIG. 31 taken along
these change gear ratios. These graphs also show that there is a
range close to the origin where the total contact point slip
distance T is small. In FIGS. 32 to 36, the lower 30% of the range
between the minimum and maximum total contact point slip distances
T at each change gear ratio is shown by a dashed line. For example,
in FIG. 32, the maximum value of the total contact point slip
distance T is 1.968 mm, the minimum value thereof is 0.818 mm, and
the lower 30% line of the range between the minimum and maximum
values is 1.163 mm. When the offset h is in the range of -0.5 mm to
0.5 mm, the total contact point slip distance T is at most 0.961
mm. The total contact point slip distance T is thus in the lower
30% range. In FIGS. 33 to 36 as well, when the offset h is in the
range of -0.5 mm to 0.5 mm, the total contact point slip distance T
is in the lower 30% range. These graphs show that setting the
offset h in the range of -0.5 mm to 0.5 mm allows the chain CVT to
be operated with the total contact point slip distance T being
small in the entire range of the change gear ratio to be actually
used. The value of 0.5 mm is 0.085 times the projected ridge length
L (5.9 mm). Setting the absolute value of the offset h to a value
equal to or smaller than 0.085 times the projected ridge length L
thus allows the chain CVT to be operated with the total contact
point slip distance T being small in the entire shift range.
[0102] In Specifications 4 as well, the offset h is set in the
range where the total contact point slip distance T is small,
namely in the lower 30% of the range between the minimum and
maximum total contact point slip distances T, as in the case of
Specifications 1, 2, and 3. In this case as well, setting the
absolute value of the offset h to 0.5 mm or less (0.085.times.L or
less) thus allows the chain CVT to be operated in the range where
the total contact point slip distance T is small.
-0.085.times.L mm.ltoreq.ha.ltoreq.0.085.times.L mm (20a)
-0.085.times.L mm.ltoreq.hb.ltoreq.0.085.times.L mm (20b)
[0103] In the case where noise is considered in Specifications 4,
such offsets ha, hb of the pins 42a, 42b that make the pitch at the
minimum running radius equal to or larger than the contact point
pitch P (7.14 mm) of the chain 16 in the linear state is 0.279 mm
or more and 0.372 mm or more, respectively, as in the case of
Specifications 1, 2, and 3.
0.279 mm.ltoreq.ha (21a)
0.372 mm.ltoreq.hb (21b)
[0104] Setting of the offset h in view of the range of the offset h
which is obtained based on the offsets h that minimize the contact
point slip distance S at the maximum running radius and the minimum
running radius and the range of the offset h which is obtained in
view of noise will be described. The offsets ha, hb of the two pins
42a, 42b are set as follows in the case of setting the offsets ha,
hb to different values. Regarding the offset ha of the pin 42a, the
range of the offset ha which is obtained based on the offsets ha
that minimize the contact point slip distance S at the maximum
running radius and the minimum running radius, namely -0.135
mm.ltoreq.ha.ltoreq.0.275 mm (Expression (17a)), and the range of
the offset ha which is obtained in view of noise, namely 0.279
mm.ltoreq.ha (Expression (21a)), do not overlap each other.
Accordingly, in the case where anti-noise measures are prioritized,
the offset ha is set to 0.279 mm that is as close as possible to
the range obtained based on the offsets ha that minimize the
contact point slip distance S at the maximum running radius and the
minimum running radius. Regarding the offset hb of the pin 42b, the
range of the offset hb which is obtained based on the offsets hb
that minimize the contact point slip distance S at the maximum
running radius and the minimum running radius, namely 0.084
mm.ltoreq.hb.ltoreq.0.498 mm (Expression (17b)), and the range of
the offset hb which is obtained in view of noise, namely 0.372
mm.ltoreq.hb (Expression (21b)), overlap each other in the range of
0.372 mm to 0.498 mm, both inclusive, and the offset hb is thus set
in this range.
ha=0.279 mm (22a)
0.372 mm.ltoreq.hb.ltoreq.0.498 mm (22b)
[0105] In the case of setting the offsets ha, hb of the two pins
42a, 42b to the same value, the offsets ha, hb are set between
0.372 mm and 0.498 mm, both inclusive, based on Expressions (18a),
(18b), and (21b).
0.372 mm.ltoreq.ha.ltoreq.0.498 mm (23a)
0.372 mm.ltoreq.hb.ltoreq.0.498 mm (23b)
[0106] In the case of setting the offsets ha, hb to the same value
based on the combination of Expressions (19a), (19b), and (21b),
Expressions (19a), (19b) and Expression (21b) do not overlap each
other, and therefore the offsets ha, hb are set to 0.372 mm that is
as close as possible to the range of Expressions (19a), (19b).
ha,hb=0.372 mm (24)
[0107] In view of both the range of the offsets ha, hb which is
obtained so that the chain CVT is operated in the range where the
total contact point slip distance T is small, namely -0.085.times.L
mm.ltoreq.ha, hb.ltoreq.0.085.times.L mm (Expressions (20a),
(20b)), and the ranges of the offsets ha, hb which are obtained in
view of noise, namely 0.279 mm ha (Expression (21a)) and
0.372.ltoreq.hb (Expression (21b)), setting the offsets ha, hb in
the common range of these ranges, namely between 0.372 mm and
0.085.times.L mm, both inclusive, can reduce slip loss and
noise.
0.372 mm.ltoreq.ha.ltoreq.0.085.times.L mm (25a)
0.372 mm.ltoreq.hb.ltoreq.0.085.times.L mm (25b)
[0108] According to the present invention, the contact point slip
distance can be reduced, and friction loss can therefore be
reduced.
* * * * *